Plastic shortenings am generally produced by thermal and mechanical treatment of several components. In conventional plastic shortenings, lightly and intermediate hydrogenated vegetable oils are blended with fully hydrogenated oils (hardstock) in varying proportions to produce a product which is approximately 85% oil and 15% solid at room temperature. The quality and texture of shortenings depend on incorporated gas, plasticity, consistency and solid to liquid ratio. The crystal phase of the fats used and the method of preparation affect these physical characteristics.
Although the beta (B) phase crystalline form of triglyceride is more thermodynamically stable than the beta prime (B') crystalline phase, plastic shortenings having a solid phase predominantly in the B' form are usually used because B shortenings tend to have a soupy, highly fluid consistency and/or a translucent appearance. It is well known in the art that B' crystals, if present, have the capacity to form a rigidly interlocking structure when suspended in a liquid component at sufficient concentration. However, plastic shortenings containing intermediate melting B' solid triglycerides are noticeably deficient in their ability to withstand storage at temperatures ranging from 90-100.degree. F. (32.degree. C.-38.degree. C.) for periods of about 1-3 months without appreciable change in their performance and appearance. Some B' plastic shortenings firm excessively and thus become difficult to blend with other constituents in normal food recipes. Shortening blends of vegetable oils and fat derived from animals are B' phase plastic shortenings. These shortenings are also high in saturates and tend to be firm. Because both the B plastic shortening and B' plastic shortening lack desired features, a compromise is often made in preparing conventional plastic shortenings. Generally shortenings crystallized in the B' phase are preferred because of their uniform product appearance and stability over varying temperature ranges.
Conventional plastic shortenings comprise intermediate-melting, partially hydrogenated semi-solid fat commonly called "intermediate-melting fat" dispersed in the liquid oil, an unhardened or partially hydrogenated liquid oil commonly called "base oil", and a fully hydrogenated solid fat commonly called "hardstock". In general, the method of attaining the B' crystal form desired for plastic shortenings is to use a suitable B' tending highly hydrogenated or saturated hardstock. Conventional B' tending hardstocks contain triglycerides that may undergo polymorphic transformations and crystal size changes on processing and storage and/or on temperature variations under stress conditions. This transformation results in a shortening which has a poor appearance, poor volume and poor performance. Further, the hydrogenation process causes trans-isomeric forms of the mono and polyunsaturates to form. There is some concern that trans isomers and saturated fats in the diet may be linked to high levels of cholesterol in the blood (hypercholesterolemia).
The use of vegetable oils and margarine for cooking and baking are thought to be an effective means for lowering dietary intake of saturated fats and trans fatty acids. A typical vegetable oil has about 2.0 grams of :saturates and 0 grams of trans per serving. Conventional margarine contains about 2.0 grams of saturated fat and 2.5 grams of trans fatty acids per serving as compared to vegetable plastic shortenings which typically contain from about 2.5 to about 3.5 grams of saturated fat and from about 2.0 to about 2.5 grams of trans fatty acids per serving. While vegetable oils and margarines are desirable from a health aspect, vegetable oil is often less desirable for baking due to lack of performance, e.g. "poor creamability". Margarines are less desirable for frying. In pan frying, margarines brown and bum, and in deep frying they are totally unusable. The browning is due to the reaction of the protein and sugars required by the margarine standard of identity.
Low trans isomer fat products (e.g., certain margarines and shortenings) are generally formed from a blend of interesterified fats, unsaturated vegetable oils, saturated vegetable oils and mixtures thereof. While these processes produce a low trans fat product, the product is often high in saturated fats. Other methods focus on reducing the saturated fat levels by utilizing the trans-isomer content of the unsaturated fatty acids to provide functional solids for the shortening or margarine.
An alternative product was made using an unhydrogenated base oil low in saturates and low in trans, a mixture of a B tending hardstock and a B' tending hardstock having an IV of less than 10, an antioxidant, an emulsifier and an inert gas. A unique processing method was required to make an effective baking and frying shortening. This shortening had reduced levels of saturates and trans fatty acids. This was accomplished predominantly by reducing the level of trans fatty acids and saturates in the base oil by using an unhydrogenated base oil and an antioxidant, which provides oxidative stability, a highly efficient structuring system and high levels of inert gas dispersed in the shortening. The B' tending hardstock is responsible for obtaining the desired B'-like behavior even though the shortening is in the B phase. The B tending hardstock stabilizes the shortening in the B phase. A hydrogenated high erucic acid rapeseed hardstock was used in this product. However, this shortening had several performance negatives. It crystallized or solidified too fast, leaving a residue of fat in the frying pan as it cooled. The melting point was too high, when baking cookies, cookie spread and browning were reduced, and the shortening texture was not optimal. When making pie crests and cookie doughs, the shortening thinned excessively during mixing.
Surprisingly, it was found that these: problems are eliminated by using a B' hardstock that is a triglyceride of palmitic and stearic acid consisting essentially of at least 65% of PSP and PSS, wherein the ratio of PSP:PSS is at least 0.8 to 1.0 and from 0 to 30% other triglycerides or synthetic fats and from 0 to 5% monoglycerides or diglycerides. PSS and PSP are defined below.
It is therefore an object of the present invention to provide a low saturate, low trans, B' stable plastic shortening suitable for use in preparation of a broad range of applications consisting of, but not limited to shortenings, peanut butter stabilizers, cosmetics, confections, frostings, baked goods, prepared cake mixes and margarine.
It is also the object of the present invention to provide a B' stable plastic shortening exhibiting superior product appearance, texture, and stability, and to provide a method for its preparation.
It is also the object of the present invention to provide a B' stable plastic shortening having a uniform consistency and which does not have a tendency to firm over a wide range of temperatures, which is stable to temperature cycling, and which does not solidify too rapidly or shear thin excessively.
Another object of this invention is to provide a method of preparation of a low saturate, low trans, plastic shortening having the above described characteristics.
These and other objects will become apparent from the following detailed description. All percentages hereto are by weight unless otherwise specified.